Typical of prior art for a wide angle lighting device would be a circular fresnel lens incandescent lamp combination as can be found on buoy lights used to navigate boats.
In these designs a fresnel or plano-convex lens is formed in the horizontal plane into a circular pattern. The lens is contoured in the vertical plane so that a single focal point is located at the center of the circular pattern. The incandescent lamp is positioned at that focal point resulting in a projected beam pattern which has a 360 degree beamwidth in the horizontal plane and minimal beamwidth in the vertical plane. in effect, the design collects light created by the incandescent source which is emitted at substantial angles above and below the horizontal plane and redirects this light into an intense beam in the horizontal plane. Since the incandescent lamp emits light in a substantially uniform spatial radiation pattern the light collected and projected by the lighting device is substantially uniform in all directions of the 360 degree horizontal beam.
This uniformity is necessary because the lighting device should be equally visible from all directions. Unfortunately, casting the lens usually creates a ridge or parting line on its surface and this parting line obstructs light passing through the lens. A second obstruction is created by wires which are used to support the filament of the incandescent lamp. Both of these obstructions tend to reduce the intensity of the projected beam at one or more locations of the 360 degree horizontal beamspread.
Another prior art design, such as described in U.S. Pat. No. 5,224,773 includes groups of light emitting diode (LED) lamps with lens top bodies assembled in circular formation with their individual concentrated light beams directed radially outward towards the circular lens. These LED lamp assemblies are used as substitutes for the incandescent lamp. These designs are inefficient because they do not collect sufficient percentages of the created light into the required beam pattern. Most of the created light is misdirected due to the bodies of the LED lamps. Also since there is only one focal point, the lens cannot properly redirect the light from each of the plurality of LED lamps.
Finally, these assemblies are enclosed in a chamber of air which has a low thermal conductivity and therefore abets their failure due to overheating.